Converging evidence suggests that children’s linguistic and
theory of mind (ToM) development are linked. Specifically,
learning the sentential complement grammatical structure has
been shown to play a causal role in the development of some
false belief reasoning skills. Here, we extend this line of work
to examine this relationship in the wild by means of a corpus
analysis of children’s speech during the typical period of ToM
development. We show that children’s use of the sentential
complement grammatical structure increases immediately
preceding the ToM development period and plateaus shortly
thereafter. Furthermore, we find that parents’ child-directed
speech follows a similar pattern.